Split-settings

- Now supporting `unicode` filenames, fixes [9](https://github.com/sobolevn/django-split-settings/issues/9)
- Tests structure is changed
- Removed example
- Changed how `MANIFEST.in` is defined

- Changed `optional` to be a function.
- Added `test_tools.py`, achieved 100% in coverage.
- Removed `setuptools-git` from `setup.py`, now `Manifest` is only way to provide `dist` sources.
- Added `run_coveralls.py` to work on both `CI` and local tests.
- Style fixes.

- Now `tox` is used for testing.
- Added `coverage` information and badge.
- Removed `pep8` utility, now using `pylint`.

- Python 3.5 support, Django 1.9 test-support, documentation updates.

- Fixed Python 3 compatibility. Fixed [7](https://github.com/sobolevn/django-split-settings/issues/7).

- Fixed issue [1](https://github.com/sobolevn/django-split-settings/issues/1): now works with Gunicorn, too